compiled-tools/kill-rogue.c

   1 /*
   2  * reaper.c: A process capable of killing `runner`
   3  *
   4  * Copyright (C) 2018 Citrix Systems UK Ltd
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation, version 2 of the
   9  * License.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19  * 02110-1301, USA.
  20  */
  21 #define _GNU_SOURCE
  22 #include <sys/types.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <signal.h>
  26 #include <stdio.h>
  27 #include <err.h>
  28
  29 int main(int argc, char ** argv) {
  30         argc--;
  31         if (argc != 2)
  32         {
  33                 errx(EXIT_FAILURE, "Usage: kill-rogue <rogue-uid> <reaper-uid>");
  34         }
  35     uid_t euid;
  36     uid_t tuid = atoi(argv[1]);
  37     uid_t xuid = atoi(argv[2]);
  38     int rc;
  39
  40     if (tuid == 0 || xuid == 0)
  41     {
  42         errx(EXIT_FAILURE, "rouge-uid or reaper-uid is 0, which should not");
  43     }
  44
  45     /* Check to make sure we have enough permissions */
  46     euid = geteuid();
  47
  48     if ( euid != 0 ) {
  49         errx(EXIT_FAILURE, "Must run as euid 0 to set uid");
  50     }
  51
  52     /*
  53      * Set euid to TARGET_UID so that we can kill the rogue 'runner'; but
  54      * set ruid to REAPER_UID so that the rogue runner can't kill us.
  55      */
  56     if ( setresuid(xuid, tuid, 0) ) {
  57         err(EXIT_FAILURE, "Setting uid to target");
  58     }
  59
  60     rc = kill(-1, 9);
  61     if ( rc )
  62         err(EXIT_FAILURE, "No processes killed");
  63     else
  64         warnx("At least one process killed successfully");
  65
  66     return EXIT_SUCCESS;
  67 }